Conventional earth current leakage circuit breakers and over-current fuses are commonly deployed to prevent injuries to people and property from dangerous conditions resulting from, for example, current leakages or fires resulting from electrical faults such as current arcs or severe current leakages. Such devices typically detect the occurrence of certain types of electrical faults to prevent harm to persons and property. However, when such conventional devices are employed, some electrical faults may not be detected and such devices may falsely detect electrical faults where none exist. Such errors may be due to the lack of intelligent ground fault and/or arc fault identification systems in conventional devices.
Ground faults may be commonly defined as the existence of a current imbalance between the supply and the return path wherein an undesirable and significant amount of the unreturned current is leaking, or passing through an object—for example a human body, to the ground. Notably, the passage of electrical current through the human body may cause injury or even death.
A current arc is typically caused by a current surging over separated or poorly contacting electrical surfaces within electrical equipment, for example, in its power cord or in an electrical device itself; or within damaged electrical wiring, such as, within the walls of a building. Current arc electrical faults may be defined as current through ionized gas between the two (e.g., supply-side and load-side) separated or poorly contacting electrical surfaces. Such current arcs are often characterized by sparking and extremely high heat, and as a result can cause electrical fires. For example, electrical fires may start when the heat and/or sparking of a current arc causes insulating material or construction material in the vicinity of the electrical fault to combust. Current arc-caused electrical fires may damage property or even endanger human life.
Unfortunately, conventional circuit breakers, fuses, or Ground Fault Circuit Interrupter (GFCI) protection devices typically cannot detect—and consequently halt—current arc electrical faults, unless a current arc produces sufficient current leakage to the electrical ground to be detected by a GFCI and/or results in a sufficient current imbalance to be detected by leakage current coil circuit. Often, an arc fault does not involve current leaking to a ground conductor or any conducting devices to the ground; it is therefore unlikely to result in a substantial current imbalance between the supply and the load.
Underwriters Laboratories (UL), an American Worldwide Safety Consulting and Certification Organization, provides criteria that ground fault detection and arc fault detection devices must meet in order to qualify as approved detection devices. Such criteria may further require such detection devices to avoid false detection of electrical faults when provided with current draws that may resemble ground faults, such as back-EMF noise or certain pulsed current draws, or may resemble arc faults. UL has also provided criteria requiring mechanisms that prevents the supply of power and/or alerts a user where detection devices are improperly installed, for example, where improper installation may hinder the effectiveness of ground fault or arc fault detection or otherwise cause the detection device to malfunction.
A combination device that protects users and electrical appliances from both ground faults and arc faults may be desired. However, existing devices that combine the functionality of both GFCIs and AFCIs operate by including substantially full sets of both GFCI circuitry and AFCI circuitry. Due to the inclusion of two sets of components, such devices may be undesirably expensive to manufacture, heavy, or have a large footprint. Improved combination or hybrid fault detection and circuit interrupter devices may be desired.
It may further be desired that such combination device comply with UL criteria governing both AFCIs and GFCIs. Because the failure to detect an actual arc fault may result in serious safety hazards, conventional apparatuses are typically over-inclusive when determining the presence of an arc fault. Such conventional apparatuses do not provide for analysis or investigation of the nature of the leakage waveform. While erring on the side of determining that electrical faults exist may have beneficial safety effects, this may increase the frequency of both false positives of arc fault detection and unnecessary tripping of circuit interrupter devices.
It may be desirable for such circuit interrupter devices to detect an end-of-life (EOL) condition. It may also be desirable for circuit interrupter devices to include locking mechanisms to provide additional protection from inadvertent resetting, and to enable an end-of-life (EOL) state, where no further reset operation is possible.
Additionally, there remains a need for a tripping mechanism to ensure a proper, flexible trip operation at the time desired. There further remains a need for such a tripping mechanism to provide automatic and/or manual testing functionality to ensure that the electrical protection devices work properly.